Lubricating oil compositions



United States Patent W 3,224,975 LUBRICATING OIL COMPOSITIONS James B. Hinkamp, Birmingham, Mich., assignor to Ethyl Corporation, New York, N.Y., a corporation of Virginia No Drawing. Filed Dec. 3, 1962, Ser. No. 241,508 2 Claims. (Cl. 252-515) This invention relates to lubricating oils particularly adapted to protect ferrous and other metal surfaces from rusting and. other types of corrosion. This invention also relates to lubricating compositions having particularly good detergent properties. Specific embodiments relate to hydrocarbon mineral oil containing a nonmetallic antirust agent and mineral oil containing both an antirust additive and a detergent of the nonmetallic type.

It is well known that lubricating oil affords only limited protection to metal surfaces and cannot be relied on to provide sufiicient protection under all conditions, especially in the presence of moisture or high humidity. Accordingly, various additives are utilized to impart to such compositions the required properties. For example, certain additives are employed to impart oxidation stability to the lubricant while other additives may be used to enhance antirust and anticorrosion properties, and

still other agents added to improve the detergent characteristics of the oil.

With conventional hydrocarbon motor oils, additives such as barium or calcium sulfonates, used primarily for their detergent properties, also serve'to provide the oil compositions with antirust protection. However, certain disadvantages are associated with the use of such metallic additives. One important factor is that when such compositions are burned, a certain amount of ash residue from the metallic constituents is left in the combustion chamber. Under normal automobile operation, varying amounts of lubricating oil bypass the piston rings and are introduced into the combustion chamber. A significent portion of the ash which is formed from combustion of the metallic additives in the oil is left behind as more volatile products are exhausted. This ash contributes to problems such as preignition, detonation, spark plug fouling, valve burning, etc.

Because of these deficiencies, it is highly desirable to reduce or eliminate the use of metallic additives in crankcase lubricating oils. Accordingly, this invention contemplates that metallic detergents are replaced with non-metallic materials. Since detergents of the latter type have essentially no antirust properties, these compositions require an antirust additive which is non-metallic and thus itself ashless.

Because the deficiencies of metallic additives have been previously recognized, certain non-metallic or ashless rust inhibitors have been developed. However, the performance of the ashless rust inhibitors of the prior art has not been entirely satisfactory. More specifically, these prior art materials have been inadequate in preventing rust under severe operating conditions over a long duration. Another problem is that many prior art materials are not compatible with other additives such as ash-free detergents. Moreover, many of the prior materials are not economically attractive.

Accordingly, it is an object of the present invention to provide improved lubricant compositions containing only relatively minor amounts of metallic additives, or more preferably compositions which are completely free of metallic additives. Another object is to provide lubricant compositions capable of protecting metal surfaces against corrosion under severe conditions. Another object is to provide lubricant compositions having improved 3,224,975 Patented Dec. 21, 1965 detergent properties. A still further object is to provide mineral oil compositions containing an antirust additive and a detergent of the non-metallic type.

The objects of the invention are accomplished by providing lubricating oil compositions containing as an antirust additive, certain pyrrolidines, and in another embodiment, lubricating compositions containing a combination of the pyrrolidine and a member of certain classes of detergents. The addition of the pyrrolidine has been found to enhance the anticorrosion properties of the lubricant. The detergents of this invention, in addition to improving the detergent and dispersing characteristics of the oil, are compatible with the antirust additive.

The non-metallic antirust additives of this invention are pyrrolidines having the formula wherein R is an aliphatic hydrocarbon group containing from about 8 to about 25 carbon atoms and having from O to 3 double bonds. As seen from the above formula, the additives of this invention are l-(aliphatic radical)-3-carboxy-5-oxo-pyrrolidines. Aliphatic hydrocarbon group R may be saturated or olefinic, and may be straight chain or branched. Thus R may be octyl, nonyl, decyl, etc., up to pentacosyl inclusive, and may be olefinic and branched counterparts of these groups. It is preferred that R be a straight chain olefinic group containing from 12 to about 20 carbon atoms, and having at least one double bond in the chain.

The pyrrolidines of this invention may be prepared in any suitable manner known to the art and such methods will not be herein discussed in great detail. One suitable method of synthesis is disclosed in US. Patent 2,757,125 and involves heating equimolar amounts of itaconic acid and an aliphatic primary amine at 200 C. There is formed the substituted pyrrolidine compound as a condensation product with the elimination of water.

While chemically pure primary amines may be used in the above reaction to form the pyrrolidine, ordinarily it is preferred to use commercial amines which are mixtures of amines of various chain lengths.

One group of such amines are derived from reduction of fatty acid mixtures such as tallow, soya, palm, and coconut fatty acid oils. From these fatty acid mixtures and ammonia are derived the corresponding fatty amines. Thus soya oil yields a mixture of amines having aliphatic hydrocarbon groups containing from 16 to 20 carbons and having from 0 to 3, predominantly 1 and 2, double bonds in the chain. Coconut oil yields a mixture of amines having alphatic groups which are predominantly saturated having from 8 to 18 carbon atoms in the chain. In commercial practice, these by-product amines are often derived from a mixture of tallow, soya, and coconut oils and thus yield a wide range of amine products. For the purpose of this invention, soya amines are preferred because the predominantly unsaturated nature of this product enhances solubility in lubricants.

Ordinarily the reaction of the amine with itaconic acid can be carried out without the use of a solvent. However, in some situations the use of an organic solvent such as benzene or ether improves the yield and purity of the product.

The concentration of ashless antitrust additive employed in the finished lubricants is, in general, from about 0.01 up to about 2.0 percent. However, due to the high effectiveness of the substituted pyrrolidines of this invention, in most applications a concentration from about 0.05 to 0.2 percent is optimum.

The rust inhibiting additives of this invention are efiective in both hydrocarbon and synthetic lubricant bases. By way of illustration typical substances in which the pyrrolidines are useful as additives include hydrocarbon mineral oil, silicone containing oils including the siloxanes and silanes, fluorocarbon oils, diester such as di-secamyl sebacate and di-Z-ethylhexyl azelate, and synthetic oils such as the polybutene oils, other polyolefin oils, polyalkylene glycol oils, and tetrahydrofuran polymer oils.

Usable lubricating oils include those derived from animal, vegetable, and mineral stocks. A preferred lubricant base comprises a mineral oil fraction of lubricating grade derived from refining a crude petroleum oil through conventional refining processes. Such refining processes include distillation, solvent extraction, clay filtration, dewaxing, acid treatment, propane deasphalting, etc. A specific and preferred embodiment of this invention comprises a crankcase lubricating oil for automotive use comprising a hydrocarbon mineral oil having a viscosity range corresponding to the Society of Automotive Engineers Classification SAE 5W through 50W containing H additives of this invention.

The improved lubricants of this invention are capable of markedly reducing the rust and corrosion which would otherwise occur with untreated lubricants. This is shown by the following test wherein treated and untreated lubricants were subjected to a modified version of ASTM D66554 Test for determining rust preventative characteristics of lubricating oil. Briefly, the test involves immersing a cylindrical steel specimen in a mixture of 300 ml. of the oil under test and 30 ml. of synthetic sea water. The test is carried out at 140 F, for 24 hours and the oil is reported as passing if duplicate specimens are rustfree at the end of the test period. Tests were carried using the above technique but with one modification. In order to make the test more severe and thereby even more critically evaluate the additives under test, 3 ml. of 0.1 normal hydrochloric acid were added to the oil-water composition.

When an additive-free lubricating oil was subjected to the above described test, heavy rusting of the steel specimens occurred and the oil was considered to have definite ly failed the test. Thereafter, the test was repeated using a lubricating composition of this invention comprising the same base oil but containing 0.1 weight percent of 1-(9- octadecenyl)-3-carboxy-S-oxopyrrolidine. ing composition passed the test, for the specimens were found to be completely free of rust. Even at lower concentrations of the pyrrolidine, the amount of rusting was markedly reduced as compared to the additive-free lubricating oil.

In another embodiment, this invention provides lubricating compositions containing a combination of a nonmetallic rust inhibitor as described above, and a non-metallic detergent additive. Detergents of this invention generally act both as detergents and dispersants. They function to prevent oxidation products and other constituents from becoming insoluble and depositing out on various engine parts. Also, any insoluble materials which may be formed are dispersed and suspended in the oil thereby minimizing settling and agglomeration of deposits. These deposits would otherwise interfere with eificient engine operation in that they are responsible for accelerated piston wear, cylinder wall wear, and also contribute to oil losses by plugging oil ring grooves.

Certain classes of detergents in combination with the antirust additives of this invention provide outstanding benefits. One class of detergents is characterized as polymers containing nitrogen substituents. These materials are copolymers of an essentially non-polar monomer which has the function of contributing to the property of This lubricatsolubility in oil (oleophilic monomer) and a monomer containing nitrogen whose function is to contribute to the surface activity of the polymer. Other monomers may be added which are innocuous with respect to these properties and merely serve to extend the polymer chain.

Examples of oleophilic monomers are polymerizable polycarboxlic acids, vinyl ethers, vinyl substituted aromatic compounds, esters of unsaturated monocarboxylic and polycarboxylic acids, esters such as alkyl acrylates and methacrylates, alkyl fumarates, dialkyl maleates etc.

The above type monomers are polymerized with a nitrogen-containing monomer such as vinyl pyridine, vinyl pyrrolidone, dialkylaminoethyl methacrylate, vinyl diethylaminoethyl ether, dialkylaminoethyl styrene, vinyl diethylaminoethyl ether, dimethylaminoalkyl methacrylamide, etc. The ratio of oleophi lic monomer to nitrogen-containing monomer is usually at least 1:1 and preferably from about 3:2 to 20:1.

A preferred group of polymers involves polymers of alkylacrylates and methacrylates with various nitrogen-- containing monomers susceptible of polymerizing and contain-ing at least one carbon to carbon double bond. These: include for example, copolymers of lauryl methacrylate and N-vinyl pyrrolidone; hexadecyl methacrylate with vinyl pyridine; lauryl methacrylate with vinyl diethylaminoethyl ether; decyl acrylate with dimethylaminomethyl styrene; and also terpolymers wherein a hydrocarbon monomer is included such as the terpolymer of lauryl methacrylate, styrene, and dibutylaminoethyl methacrylate.

One particularly outstanding group of detergents of this invention comprises the copolymers of alkyl methacrylates and a nitrogen-containing monomer selected from the group consisting of dialkylaminoethyl methacrylates, N- vinyl pyrrolidones, and vinyl pyridines. These polymers have the repeating structure F l r a.

wherein R is an alkyl group having from about 8 to about 25, preferably 12 to 18 carbon atoms n is an integer ranging from 1 to about 50, X is selected from the group consisting of acids.

oil in an amount ranging from 0.1 to about percent, preferably from about 3 to 8 percent.

Another preferred group of detergent-dispersants are N-substituted alkenyl heterocyclic imides. These compounds are obtained by reacting a hydrocarbon polymer, preferably the polymer of an olefin having from 2 to 5 carbon atoms, with an acid anhydride, followed by reaction with a compound having an amino function to form the heterocyclic imide. An outstanding example is a detergent formed by reacting a polyisobutene having a vmolecular weight of about 200 to 1500 with an acid Rs N '--RzN GE -C R4 or with N-(aminoalkyl)piperazine to form N-alkylpiperazine monoalkenyl succinimide,

O R CH(% CH2-CH2 NRzN NH CH CH:

CHPEIJ In the above formulae, R is a polyolefin radical having a molecular weight of from about 200 to 1500 derived from olefins having from 2 to 5 carbon atoms, R is a hydrocarbon group having from 1 to about 5 carbon atoms, and R and R are alkyl groups containing from 1 to about 12 carbon atoms.

Another class of detergent-dispersants usable in combination with the ashless antirust additives are reaction products of higher polyhydric alcohols with carboxylic Especially preferred are reaction products of the hexahydric alcohols mannitol, sorbitol, and dulcitol with higher fatty acids having from about 12 to 20 carbon whereas reaction in the presence of sodium hydroxide yields predominantly sorbitan esters.

One method of producing these products is disclosed in US. Patent The most preferred dispersants from the above class are the sorbide esters, especially the monoesters derived from reaction of sorbitol or sorbide with a fatty acid having from 12 to about 20 carbon atoms and containing up to 3 double bonds. Particularly outstanding are the properties of sorbide monooleate. This product is obtained by reaction of sorbitol with oleic acid in the presence of phosphoric acid at a pH of 12 at a temperature of from about 15 0-3 00 C.

Another class of detergents usable in my compositions are alkylphenol-olefin oxide condensation products. The condensation to yield these products is carried out in the presence of a catalyst such as sodium methoxide at temperatures of about 200 C. The molar ratio of phenol to olefin oxide is from about 1:1 to 1:100, preferably from 1:1 to about 1:20. The overall reaction may be represented as follows:

where R is a polymethylene group, preferably ethylene of propylene, R is an alkyl group having from 6 to 20 carbon atoms, R is selected from the group consisting of hydrogen and alkyl groups having from 6 to 20 carbon atoms, and x is an integer ranging from 1 to 100. A preferred group of detergents are the condensation products of propylene oxide and p-tertiary-octylphenol reacted in a molar ratio of from 1:1 to 20:1.

Certain fatty acid alkanolamides constitute another group of detergents that can be used in combination with the ashless antirust additive. These are the reaction products of equimolar amounts of an alkanol amine with a fatty acid heated at from about 150 to 250 C. for from 1 to 4 hours in a nitrogen atmosphere. These products have the general formula wherein R is the organic residue of a straight chain fatty acid containing from 10 to about 20 carbon atoms in the molecule, and R and R are the same or different and are the organic residue of aliphatic alcohols having from 1 to about 8 carbon atoms in the molecule. Preferred products are those wherein R contains from 11 to 17 carbon atoms and R ad R are the same and contain from 2 to 4 carbon atoms. Thus, compounds such as lauric diethanolamide, oleic diethanolamide and linoleic diethanolamide are preferred.

Lubricant compositions containing an antirust additive and detergent additive of this invention were subjected to a modified version of the Polyveriform Test to deter mine their sludge forming tendency. The original test was described in a paper entitled, Factors Causing Lubricating Oil Deterioration in Engines, Industrial and Engineering Chemistry, Anal., Ed. 17, 302 (1945). The test consists of bubbling air at a rate of 47 liters per hour through grams of the lubricant for a period of 48 hours. The test is carried out at a temperature of 300 F. The test was modified in that the steel sleeves and copper test piece described in the original test were not employed. Also, oxidation catalysts comprising 0.1

Weight percent lead bromide, and copper-lead bearings (1" x 2%") are included in the oil rather than ferric ethylhexoate as described in the original test. This modification not only makes the test more stringent but the results have been found to better correlate with the standard L-38 engine test. After the 48 hour test period, the oil is cooled and graded visually for any sludge that may have been formed. A rating of A+ indicates no visible sludge and a rating of E indicates extremely heavy sludge. The oil is also subjected to an acid number determination and any viscosity increase is measured. Also, the bearings which were included in the oil medium are weighed and any loss in Weight isnoted. A high bearing weight loss indicates the presence of significant amounts of organic acids produced from oil oxidation and deterioration.

An additive-free mineral oil, thesame oil containing additives of this invention, and a commercially available ashless oil containing a full complement of ashless additiv'es were submitted to the above described Polyveriform Test. The composition of this invention comprised mineral oil containing 0.1 weight percent of 1-(9-octadecenyl)-3-carboxy-5-oxo-pyrrolidine; 5 percent of a polymeric detergent of this invention obtained by polymerizing a methacrylate with a nitrogen-containing monomer; 0.4 weight percent of an antiwear additive; and 0.6 weight percent of a phenolic antioxidant. T-he polymeric detergent in this composition is available commercially from the Rohm and Haas Company under the trade name Acryloid 917, and is believed to be a copolymer of an alkyl methacrylate and diethylaminoethyl methacrylate. The results of these tests are shown in Table 1.

TABLE 1.POLYVERIFORM TEST RESULTS The above tests show that the additive-free mineral oil was susceptible to sludge formation and also susceptible to a high degree of viscosity increase. As evidenced by the relatively high acid number and large bearing weight loss, the base oil was also susceptible to oxidation with the production of undesirable organic acids. The corn mercial oil, which contained ashless additives to impart the desired characteristics to the oil showed an improvement over the base oil. However, there was evidence of a small amount of sludge formed and a significant viscosity increase and bearing weight loss was noted. The compositions of this invention showed an improvement in each criteria over both the base oil and the commercial ashless oil. As indicated by an A-|- rating, sludge was essentially absent; only a relatively minor increase in viscosity was noted; and bearing weight loss and the acid number were very low. Thus the compositions of this in vention are clearly superior to the base oil and to the commercially available ashless oil.

The results of the several tests described above clearly show that the substituted pyrrolidines of this invention are effective in protecting metals against rust and also that compositions of this invention containing the combination of an antirust additive and detergent have a minimum tendency to form sludge, show only a minor increase in viscosity and are resistant to oxidation thereby resulting in a minimum amount of undesirable organic acids being produced.

Some typical compositions of this invention are shown in Table 2.

The antirust agents and the detergent-dispersants of this invention, while being highly suitable for addition directly to the finished lubricating oil, may also be incorporated into ashless packages. Such packages are concentrates of various ashless additives dispersed in oil to be added as a whole to the finished lubricating oil. Thus an embodiment of this invention is an ashless concentrate comprising a carrier oil, preferably mineral oil, containing a high concentration of an antirust additive and also oil containing a combination of the antirust additive and a detergent-dispersant of this invention. The oil may contain as high as 50 percent additives, depending on the solubility of the particular additives employed. Usually it is preferred to use concentrates wherein the combination of additives are present in a concentration of from about 20 to 40 percent. Examples of such concentrates are shown by Examples 16 and 17 above.

The compositions of this invention can also contain other additives commonly used in the lubricant art to improve various characteristics of lubricants. While greatest benefits are obtained from oil compositions completely free of metallic additives, the additives of this invention are still efiective in oils containing significant amounts of metal-containing additives and can be so used. With crankcase lubricants, some of the metallic additives that may be used include antioxidants such as zinc dialkyldithiophosphate, metal carbamates such as zinc dibutyldithiocarbamate; metal salts such as calcium cetylphenate; dispersant-detergents such as sulfonate or phenate salts of barium or calcium; antiwear agents such as dialkyltin sulfides, lead naphthanate, etc.

While in some cases amounts of metal-containing additives may be employed, the preferred crankcase lubricants are completely free of metallic additives. Other ashless additives that can be incorporated into the concentrate or added directly to the oil include among others, oxidation inhibitors. These additives are widely used to decrease the amount of oxygen taken up by the oil thereby reducing the formation of acidic materials. The inhibitor may also terminate oil oxidation by formation of inactive soluble compounds, or the inhibitor itself may be oxidized in preference to the oil. Usable inhibitors include organic amines such as diphenyl amine, phenylnaphthylamine,

TABLE 2.LUB RICANT COMPOSITIONS OF THIS INVENTION Antirust Additive Example Lubricant Base Dotergcnt-Dispcrsant Wt,

Aliphatic Substituent of 1- Wt. Percent (aliphatic radical)-3-earboxy- Percent 5-oxo-pyrr0lidine Hydrocarbon mineral oil 0. O5 Hydrocarbon mineral oil 0. l Hydrocarbon mineral oil 2. 0 Hydrocarbon mineral oil 0. 4

Hydrocarbon mineral oil O. 01 Hydrocarbon mineral oil Mixture (percent) 0.25

Q-Octadecenyl 9.12-octadecadienyl (4). Hexadecyl (29). Octadecyl (20). Tetradecyl (2). 7 Hydrocarbon mineral oil Mixture (percent) 0.1 Sorbidc monooleate 4 Q-Octadecenyl (33). 9,12-octadecadienyl (52). 9,1(21315-octadecatrienyl Hexadecyl (8). Octadeeyl (2). Eicosyl (1). 8 Hydrocarbon mineral oil 9-0ctadecenyl 0. 1 Copolymer oflanryl methacrylate and diethylan i. 10

noethyl methacrylate. 9 Hydrocarbon mineral oil Mixture of Example 6 0. 05 N-propylpiperazine polyisobutenc suceinimide. 5 10 Hydrocarbon mineral oil Mixture of Example 7 0. 1 N-di ricthylaminopropyl polyisobutene Succini- 3 1111 e. Di'2-ethyl-hexyl-sebacate 9-0ctadecenyl 0.1 None Polyrnethyl siloxane Mixture of Example 6. 0. 7 Sorbide monooleate 4 Poly'fluorocarbon oil 9-0ctadecenyl 0. 8 copolyilngr of hexadecyl methaorylate and N m l 3 pyrro 1 one. Tetraalkyl silane" Lauryl- 0. 2 Laurie diethanolamide 0, 1 Polyalkylene glycol Eicosyl 0. 4 Condensation product of p-tert-octyl phenol with 5 propylene oxide. Hydrocarbon mineral oil Mixture of Example 7. 2. 0 Colpolymer of lauryl mcthaerylate and vinyl pyri- 35 1116. Hydrocarbon mineral oil 9 oetadceenyl 1. 7 N-dirlnethylaminopropyl polyisobutene u i i- 20 tetramethyl diaminodiphenylmethane, lecithin, alizarin; sulfur compounds such as sulfides, hydroxysulfides, thioethers, sulfurized terpenes such as sulfurized pine oil, sulfurized wax olefins, sulfurized sperm oil; halogen compounds and phosphorus compounds such as the addition products of phosphorus pentasulfide with a polyolefin such as terpene; phosphorus compounds such as tributyl phosphite, triphenyl phosphite, etc. Antioxidants are usually added to lubricating oil at a concentration ranging from 0.05 to 2 percent, usually from 0.3 to 1.0 percent.

It is preferred to use as antioxidants phenolic derivatives. These include substituted phenols such as the cresols, di and tri-alkylated phenols substituted with alkyl groups such as ethyl, propyl, and butyl. Highly preferred compounds are the sterically hindered phenols wherein at least one tertiary alkyl substituent is positioned ortho to the hydroxy group. Examples are 2,6-di-tertiary alkyl phenols, especially 2,6-di-tertiary butylphenol. I can also use biphenyl derivatives containing hydroxy and alkyl substituents. Other usable phenols are methylene bisphenol derivatives, such as 4,4-methylene bisphenol, and similar compounds substituted with lower alkyl groups. Outstanding among the latter type are the symmetrical sterically hindered phenols such as 4,4-methylenebis (2,6-ditertiary butylphenol).

'I can also use methylene bisphenols wherein the methylene group has substituents thereon such as alkyl groups or another aromatic nucleus, also bisphenols wherein the aromatic nuclei are joined by a polymethylene group may be used. Other compounds that may be used as antioxidants are phenol ethers and sulfur bisphenols, i.e., wherein the aromatic nuclei are joined by sulfur.

Other additives that may be included are extreme pressure and antiwear additives. These compounds are useful in reducing friction, scoring, and wear of contacting metal parts. Such additives often contain chlorine, phosphorus, and sulfur. Illustrative of these compounds are chlorinated waxes, organic phosphites and phosphates such as tricresyl phosphate, etc. A preferred group of these additives comprises phosphonates having the formula wherein R and R are alkyl groups having from 1 to about 8 carbon atoms. In a particularly outstanding embodiment, both R and R are secondary alkyl groups having from about 3 to 6 carbon atoms. These compounds are usually included in a concentration of from 0.1 to 1 percent.

Metal deactivators may also be included in my compositions. This class of compounds may act by either precipitating dissolved metal ions out of the oil, or by forming inactive complexes with the metal compounds. Also, the deactivator may function passively by forming an inactive film on the metal surface. Commonly used metal deactivators include complex amines and sulfides, mercapto-benzothiazole and zinc dibutyl-dithiocarbamate. Concentrations of these additives usually range from about 0.05 to 0.2 weight percent.

Pour point depressants are used to prevent growth and crystallization of waxy constituents at reduced temperatures thereby lowering the pour point of the oil. Commonly used materials for this purpose include complex condensation products of paraffin wax and naphthalene, prepared by chlorinating the wax and condensing it with naphthalene by Friedel-Crafts reaction; condensation products of chlorinated wax with phenols; high molecular weight polymerization products of esters of methacrylic acid and higher fatty alcohols such as cetyl, lauryl, etc.

My compositions may also contain viscosity index improvers which lower the rate of change of viscosity with temperature. These materials include polymerized olefins and isoolefins, especially butylene polymers. Also usable for this purpose are methacrylic acid ester polymers and alkylated styrene polymers. Foam inhibitors to prevent formation of stable foams may be included. An outstanding example are the silicone polymers. In addition other additives such as dyes and color stabilizers may be included in the compositions. The latter materials include certain hydroquinones, dithiocarbamates, aliphatic amines, dicyclohexyl amines, etc.

It is to be understood that although specific classes of ashless detergent-dispersants have herein been described, other classes of such additives can be included in the compositions of this invention. Any ashless detergent which is compatible with the antiwear and antirust agents of this invention and which has the requisite solubility can be included either in combination with the detergents herein described or in place thereof. The detergents may be of the polymeric type such as alkyl methacrylatemethacrylic acid polymers and .these polymers esterified with polyols such as pentaerythritol and polyethylene gly col; of the polyester type such as polyesters of dibasic acids or anhydrides with diethanolamines, i.e., polyesters of alkenylsuccinic anhydride with alkyldiethanolamines; or they may be monomeric compounds such as aromatic dialkanolamines, i.e., mixed xylyl dipropanolamines; etc.

I claim:

1. A lubricant composition comprising a major proportion of a lubricating oil and from 0.01 to about 2 percent by Weight of l-(aliphatic radical)-3-carboxy-5-oxopyrrolidine wherein said aliphatic radical is a hydrocarbon group containing from 8 to about 25 carbon atoms.

2. The composition of claim 1 wherein said aliphatic radical contains from 12 to about 20 carbon atoms and up to three double bonds.

References Cited by the Examiner UNITED STATES PATENTS 2,403,067 7/1946 Fischer et al 2525 1.5 2,757,125 7/1956 Mudrak 16793 2,843,548 7/1958 Westlund et al. 2525l.5 X 2,898,299 8/1959 Lowe 25246.6 2,908,711 10/1959 Halter et a], 2525l.5 3,018,250 l/1962 Anderson et al. 2525l.5 3,024,195 3/1962 Drum-mond et al. 2525l.5 3,030,303 4/1962 Ryan 2525l.5 X 3,043,775 7/1962 Coffield et al. 252 52 3,123,570 3/1964 Bonner et al. 25252 X FOREIGN PATENTS 525,894 6/1956 Canada.

DANIEL E. WYMAN, Primary Examiner. 

1. A LUBRICANT COMPOSITION COMPRISING A MAJOR PROPORTION OF A LUBRICATING OIL AND FROM 0.01 TO ABOUT 2 PERCENT BY WEIGHT OF 1-(ALIPHATIC RADICAL)-3-CARBOXY-5-OXOPYRROLIDINE WHEREIN SAID ALIPHATIC RADICAL IS A HYDROCARBON GROUP CONTAINING FROM 8 TO ABOUT 25 CARBON ATOMS. 